1. Technical Field
The present disclosure relates to a circuit board for COF (Chip on Film) package, and more particularly, to a circuit board for COF package, where routing patterns for transmitting signals or power are formed and an integrated circuit is mounted.
2. Related Art
Recently, flat panel display devices using a variety of light sources have been released on the market. Representative examples of the flat panel display devices may include an OLED (Organic Light Emitting Diode) display device.
The OLED display device is a self-luminous display device that displays an image using an OLED.
In general, the OLED display device includes a plurality of pixels, a display panel configured to display an image, a driving unit configured to display a driving signal to the display panel, and a power supply unit configured to supply a voltage for image display and a voltage for operation to the display panel and the driving unit, respectively.
The driving unit may be divided into a timing controller, a source driver and a gate driver, and embodied by a packaged chip or integrated circuit. The source driver and the gate driver, which are included in the driving unit, provide a source signal and a gate signal to the display panel, and are electrically connected to a printed circuit board on which the display panel and the power supply unit are mounted in the form of a TCP (Tape Carrier Package), COF (Chip on Film) or COG (Chip on Glass) package.
Among the packages, the COF package has a structure in which an integrated circuit is mounted on a circuit board, and the circuit board has a structure in which routing patterns for transmitting a signal or power to a base film made of an insulating and flexible material are formed. The COF package has a low thermal expansion coefficient, exhibits excellent flexibility, uses a slim base film, and has the routing patterns formed at a fine pitch, compared to the TCP package. Thus, the use of the COF package is increasing.
In the COF package, the integrated circuit mounted on the circuit board may receive an external signal or power through a routing pattern of the base film, and the circuit board may include routing patterns for various uses.
The integrated circuit may be internally divided into a digital part such as a shift register and an analog part such as a buffer for processing a signal outputted from a digital-analog converter. Between the digital part and the analog part, a part sensitive to an interference of coupling noise may be defined as a core block.
When a routing pattern is formed on the circuit board corresponding to the core block of the integrated circuit mounted on the circuit board, coupling noise caused by a signal or voltage of the routing pattern may have an influence on the core block.
The coupling noise may have an influence on the operation of the core block, and serve as a factor which causes a malfunction of integrated circuit in a serious case.
In the OLED display device, the pixels of the display panel require a supply of pixel supply voltage including a high-potential pixel supply voltage EVDD or low-potential pixel supply voltage EVSS for their operations. The supply of the pixel supply voltage needs to be implemented on the COF package having a limited area. Thus, the above-described coupling noise is highly likely to have an influence on the operation of the core block in the integrated circuit.
Therefore, there is a demand for design of a circuit board which is capable of preventing an interference with the core block of the integrated circuit mounted on the circuit board.